Coded track circuit signalling system for railways and the like



J. R'COLEY 2,418,869

CODE-D TRACK CIRCUIT SIGNALLING SYSTEM FOR RAILWAYS AND THE LIKE April15, 1947.

Filed June 27, 1944 Md m@ .m .p A w a 52 2 m Patented Apr. 15, 1947CODED TRACK CIRCUIT SIGNALLING SYS- FEM FOR RAILWAYS AND THE LIKE JamesPerrin Coley, London, England, assignor, by mesne assignments, to TheUnion Switch and Signal Company, Swissvale, Pa, a corporation ofPennsylvania Application .lune 27, 1944, Serial No. 542,338 In GreatBritain November 5, 1942 This invention relates to track circuitsignalling systems of the kind in which the track rails of a blocksection are arranged to be supplied with coded signalling currentconsisting of current impulses separated by intervals the frequency ofthese impulses being controlled in accordance with traflic conditions inadvance, a track relay at the entrance end of the section beingresponsive to this coded current and arranged to control a signal atthis end of the section.

The invention furthermore relates to systems of the character abovedescribed in which, during the intervals between the current impulses,signalling current impulses are arranged to be fed to the track rails atthe entrance end ofthe section to operate a relay at the exit end, thisrelay being arranged correspondingly to control approach locking orother control circuits.

Signalling systems of this kind have previously been proposed, but, ashitherto arranged, are open to the disadvantage that. to ensure safetyin operation, the coded s gnalling current impulses operating the relayat the entrance end of the section (hereinafter termed the master codecurrent) must be supplied to the track rails at the exit end of thesection. Since the other current impulses for controlling the relay atthe exit end of the section (hereinafter termed the feed back current)are, for the same reasons, necessarily supplied to the track rails atthe entrance end, a supply of current is required at both ends of thesection.

The present invention has for its object to avoid this disadvantage andto simplify the apparatusrequired and according to the prin i al featureof the invention a suooly of signalling current is connected to thetrack ra ls at the entrance end only of the track section (in parallelwith the track relay at that end). the rails at the exit end of thesection being connected together through a rectifier at intervals with afrequency controlled in accordance with traffic conditions in advance,so as to provide master code current impulses in the track rails which,also 'at the exit end of the section, are arranged to be connected tothe relay responsive to the feed back current .during the intervalsseparating the master code impulses. These connections are preferablyeffected by a relay, the energising winding of which is supplied withcurrent impulses at the master code frequency, this relay when energisedeffecting the connection of the track rails together through therectifier and, when released, effect- 3 Claims. (Cl. 246-34) ing theconnection of the feed back relay to the track rails.

The invention is illustrated by way of example in the accompanyingdrawing the single figure of which is a diagrammatic view of a simplesignalling system for a single track section embodying one form of theinvention.

Referring now to the drawing it Will be seen that the track sectioncomprises a pair of track rails l, 2 insulated from one another and fromthe rails of the section's ahead and to the rear of the section in theusual manner, a signal SI ad jacent to the entrance end of the sectionwhile a. signal S2 adjacent to the exit end controls the admission oftrafiic into the track section ahead.

At the entrance end of the section a code following track relay CFR isconnected across the track rails l, 2 which are also connected at thispoint through conductors 3, 4 to the terminals of the secondary winding5 of a transformer T, a suitable limiting resistance or impedance 6being connected in this circuit. The primary winding 7 of thetransformer T is connected to the terminals BX, NX of a suitable sourceof alternating current supply and the track relay contacts 8 control theoperation of decoding apparatus DA adapted in the usual manner tocontrol in turn relays HR, DR controlling the signal SI at the entranceend of the track section.

The code following relay CFR is a direct current relay and preferably ofthe bias polar type but other types can be used. The arrangement is suchthat relay CFR picks up its armature con tact member 8 when the relay isenergised by'director rectified current of a given polarity such aspositive polarity, and the contact member 8. is released to its biasedposition when the relay is energised by direct current of negativepolarity or is deenergised and also when alternating current is suppliedto the relay because the relay does not respond to alternating current.

At the exit end of the section a, master code transmitting relay CTP isprovided adapted to be supplied with energising master code currentimpulses in the usual manner at a frequency dependent upon trafficconditions ahead. For example these current impulses may have afrequency of or '75 per minute dependant upon. when the signal S2adjacent to the exit end of the section and controlled from a signalcabin is indicating clear or caution.

As shown in the drawing this action is effected by means of anelectro-magnetically operated codetransmitter CT comprising armatures 9and l cooperating with contacts H and I2 respectively and adapted whenthe transmitter CT is energised to oscillate the armature 9 at afrequency of 180 per minute and the armature Ill at a frequency of 75per minute. The armatures 9, H! are electrically connected together andto a conductor l3 leading to the energising winding of the relay CTP.

The front contacts H, I2 of the transmitter CT are connectedrespectively to the front and back contacts l4, l5 of a relay (notshown) controlling the signal S2 and having an armature lfi adapted tocooperate with the contacts M. H). Operating current for the relay CTPis supplied through the circuits indicated on the drawing from supplyterminals BX and NX.

The transmitting relay CTP is provided with armatures l1 and I8 adaptedto cooperate with front contacts I9, 20 respectively which, when therelay CTP is energised, connect the track rails I, 2 of the sectiontogether through conductors 2|, 22, the armatures ll, i8, front contactsI9, 20 and a rectifier RI. The relay CTP is also pro vided with backcontacts 23, 24 which when the relay CTP is released connect the trackra ls I, 2 to the output terminals 25, 26 of a bridge connectedrectifier R2 the output terminals 21, 28 of which are connected to theenergising winding of a feed back relay RCFR. The latter is providedwith an armature 29 cooperating with a front contact 30 which when therelay RCFR is energised effects the supply of energising current to aslow-releasing relay FSR while when the relay RCFR is released,energising current is fed through a back contact 3| to a secondslowreleasing relay BSR through a front contact 32 of the relay FSR. Therelay BSR. is arranged to control in any desired manner approach lockingor other circuits for the track section ahead as indicatedconventionally in the drawing.

The operation of the system is as follows:

Assuming that the track section is unoccupied by a train or vehicle andthat master code current impulses are being supplied by the transmitterCT to the transmitting relay CTP at the exit end at a frequency of 180or '75 per minute according the the setting of the signal S2 adjacent tothis end of the section and the corresponding position of the armature16, it will be evident that during a current impulse when thetransmitting relay CTP is energised, a circuit will be completed fromone terminal of the secondary winding 5 of the transformer T at theentrance end through track rail conductor 3 and resistance 6, the trackrail 1, conductor 2!, armature ll of relay CTP, front contact I9, therectifier RI, front contact 23, armature l8 conductor 22, the othertrack rail 2 and conductor 4 to the other terminal of the transformerwinding 5,

The rectifier RI is poled to pass in its forward or low resistancedirection one half cycle, say, the negative half cycle, of thealternating current and to substantially block the other or positivehalf cycle of the current. Thus during the code interval the relay CTPis picked up connecting rectifier Rl across the rails the negative halfcycles of the alternating current are shunted away from relay CFR andthe positive half cycles are not, and relay CFR is energised to Pick upits armature contact member 8 by such impulses of rectified current.During the code interval relay CTP is released to disconnect rectifierRI and to connect relay RCFR to the rails through rectifier R2, bothhalf cycles of the alternating current are applied to relay CPR and thatrelay is deenergised to release its contact member 8 since the relayCFR. is non-responsive to alternating current.

The code following relay CFR at the entrance end will accordingly beenergised and deenergised at the frequency of the master code and,through the decoding apparatus DA, and the relay HR or DR will cause acorresponding indication to be given by the signal St at the entranceendof the track section.

During the intervening periods or intervals when the transmitting relayCTP is deenergised, current from the secondary winding 5 of thetransformer T will be supplied through the track rails I, 2 conductors2|, 22, armatures l1, l8 and back contacts 23, 24 of relay CTP, therectifier R2 to the feed back relay RCFR at the exit end. Relay RCFR isa direct current relay and is energised and picked up in response tothis impulse of rectified current supplied through the rectifier R2.That is, relay RCFR and rectifier R2 form a code following meansresponsive to the impulses of alternating current. It is clear thatother forms of alternating current relays can be used. When relay RCFRis energised, the slow-releasing relay FSR. will also be energised,through a circuit including armature 29 and front contact 38 of relayRCFR but relay FSR will not release as relay RCFR is deenergised whenrelay CTP again picks up. Accordingly the other slowreleasing relay BSR.will be energised through a circuit including armature 29 and backcontact of relay RCFR and front contact 32 of relay FSR when relay RCFRis deenergised. These two relay FSR and BSR will remain picked up solong as master code current is supplied to the track rails I, 2. Theapproach locking or other circuits controlled by the slow releasingrelays FSR and BSR will accordingly be energised or deenergised.

In the event of a train or vehicle entering the track section the trackrails I, 2 and the code following relay CFR at the entrance end of thesection will be short-circuited so that the signal SI will be caused toindicate danger While since current is no longer supplied through thetrack rails I, 2 to the feed back relay RCFR at the exit end of thetrack section even during the intervals when the transmitting relay CTPis released, the feedback relay RCFR will be permanently deenergised andthe slow-releasing relays FSR and BSR will, consequently, eventuallyrelease with a corresponding efiect on the approach locking or othercircuits controlled thereby.

The invention is evidently not limited to the particular system abovedescribed and illustrated. For example, the master code transmittingrelay CTP may, if desired, be dispensed with, the connections effectedby this relay being eifected by contacts provided for this purpose onthe code transmitter CT or its equivalent instead of through the actionof the relay CTP.

Having now described my invention, what I claim as new and desire tosecure by Letters Patent is:

1. In a track circuit for a track section, the combination comprising, asource of alternating current and a direct current code following relayconnected in multiple across the rails at one end of said section, arectifier, an alternating current code following relay means, and acoding device operable to alternately connect said rectifier and saidalternating current code following relay means across the rails at theother end amasco of the section to operate both said direct current codefollowing relay and said alternating current code following relay meansat the code rate predetermined by the rate of operation of said codingdevice.

2. In a track circuit for a track section, the combination comprising, asource of alternating current, a first code following relay, said sourceand relay connected in multiple across the rails at one end of thesection, a second code following relay, a rectifier, coding meansoperable to a first and a second position, and means to connect saidrectifier and said second relay to the rails at the other end of thesection through first and second position contacts respectively of saidcoding means, whereby said first code following relay is energised byrectified current each code interval said rectifier is connected to therails and said second relay is energised by alternating current eachcode interval that relay is connected to the rails when the section isunoccupied.

3. In a track circuit for a, track section through which trafficnormally moves in a given direction, the combination comprising, asource of alternating current and a direct current code following relayconnected in multiple across the rails at the entrance end of thesection, a half wave rectifier, an alternating current code followingrelay means, and a coding device operable to alternately connect saidrectifier and said alternating current cod following relay means acrossthe rails at the exit end of the section to operate both said directcurrent code following relay and said alternating current code followingrelay means at the code rate predetermined by the rate of operation ofsaid coding device when the section is unoccupied and such operation isdiscontinued when the section is occupied due to the shunting of therails.

JAMES PERRIN COLEY.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Place 1 Dec. 5, 1939

